1. Field of Invention
The present invention relates to a tool for inspecting broken wafer edges. More particularly, the present invention relates to a wafer inspection tool capable of assisting in finding the cause of broken wafer edges.
2. Description of Related Art
In the manufacturing of conventional semiconductor devices, sputtering methods can be used to deposit thin films because of their good step coverage capability. In fact, sputtering methods are quite often used to deposit metallic layers and barrier layers. Normally, a sputtering machine has a number of different chambers to carry out different sputtering programs for achieving different goals.
In general, each wafer in a sputtering chamber is fixed in position by a number of clamp pins. However, the pressure caused by these clamp pins can sometimes break off tiny pieces from the edges of a wafer. These broken wafer edges have a tendency to retain a residual amount of the chemical reagents used in subsequent processes. Consequently, quality of the finished product may be affected.
As a normal sputtering machine (for example, an Endura machine) may contain a few chambers, broken wafer edges can be discovered only when the last stages of the processing operation have been completed. Whenever broken edges are discovered on the wafer, it is very difficult to determine where they happened. For example, the broken edges may or may not be caused by the sputtering machine. Furthermore, even if we are certain that those broken edges are caused by the sputtering machine, it is still very difficult to trace the cause to a specific set of clamp pins in a particular chamber.
The conventional method of tracing the cause in the sputtering machine is to lower the temperature and release the vacuum in one chamber. Then, the chamber is opened up to see if the clamp pins in that chamber caused the broken edges. If broken edges are not caused by that particular chamber, vacuum in the chamber has to be reestablished and the chamber has to be heated up again so that the previous operating state of the chamber is regained. However, raising temperature inside a chamber takes a long time. Therefore, whenever a particular chamber is down to check for the cause of broken edges, subsequent processing operations will be affected and productivity will be lowered.
In summary, the conventional method of lowering and raising the temperature in each chamber in turn to check for the cause of broken edges on a wafer is both time-consuming and rather indefinite. Moreover, subsequent processing flow may be affected.
In light of the foregoing, there is a need to provide some tools for determining the cause of broken edges on a wafer.